Reinforcing cable having increased degree of bonding

ABSTRACT

The invention can be used in the production of prestressed reinforcement. The problem of interest consists in developing a reinforcing cable having an increased degree of bonding, said cable having guaranteed structural stability and providing an increased degree of bonding with concrete, durability, and stress relaxation resistance. In a reinforcing cable, a central wire ( 1 ) is disposed along the axis of the cable, and is configured with spiral grooves ( 2 ) having a pitch that is equal to the pitch of the lay of the cable. Strand wires of an inner layer are disposed within the grooves, each of said wires being in contact with the central wire and with two adjacent wires of the inner layer. Strand wires are helically arranged at equal intervals from one another in an outer layer, each of said wires being disposed in a groove between the strand wires of the inner layer, and being in contact with the latter.

The invention relates to cable production and can be used in the production of prestressed reinforcement designed for prestressing by means of abutments and poststressing with injection of channels.

A seven-wire reinforcing cable according to GOST R 53772-2010 is known, which consists of a central wire with a smooth surface and six strand wires with a periodic profile in the form of crescent-section depressions under a cylindrical generatrix of the wire surface, arranged in three longitudinal rows, wherein the strand wires are helically arranged around the central wire in one concentric layer in which each strand wire is in contact with the central wire and two adjacent strand wires.

The disadvantage of this design is the relatively low degree of bonding with concrete. Although the known cable formally has additional mechanical bonding in the screwing direction, however, in general, does not provide high degree of bonding with concrete due to the low height of the elements of periodic profile which do not allow to maintain mechanical bonding during Poisson narrowing of the cable when tensioned under the action of the load applied to reinforced concrete. In addition, the described elements of periodic profile transfer the stress of the reinforcement by means of bearing/shear loading to the concrete fragments directly located in the depressions, transferring the load to the block by means of tangential stresses. Also, the low degree of bonding is due to narrow intervals between the circle circumscribed around the cable section and the surface of the outer wires which do not leave space for the formation of strong concrete ridges under the cable generatrix. Another disadvantage of the known reinforcing cable is a decrease in durability and relaxation resistance compared with a similar cable made of plain wires. This is due to the fact that the periodic profile forms numerous stress concentrators, which reduce the mechanical properties themselves and, in addition, the periodic profile on the contact surfaces causes point contact between adjacent wires, which further increases stress concentration, and also reduces the relaxation resistance because of the local introduction of adjacent wires into each other at the contact points and of the resulting displacement to a smaller radius of laying and a direct increase in the length of the wires, leading to an increase in the length of the cable when used in structures and, as a consequence, to a decrease in pretension.

The closest prior art of the cable according to the present invention is a reinforcing cable according to patent RU 2431024, comprising a central wire and strand wires with a periodic profile, helically wound around it. The periodic profile is provided in the form of inclined protrusions above the generatrix of the cable reduced surface, and the areas of the surface of the wires, being in contact with other wires, are provided in the form of helically arranged flat planes. The periodic profile is applied on the outer area of the surface of the strand wires, and the intervals between the circle circumscribed around the cable section and the surface of the outer wires have increased dimensions compared with the intervals in the circular wire cable due to the shape of the section of the wires and the arrangement of the wires having areas extending onto the outer surface of the cable in two layers such that the contour connecting tangentially the outer areas of the strand wires is approximated to a triangle with rounded corners.

The known cable has a high degree of bonding due to the developed inclined surfaces formed by a spiral-twisted triangular section, which allows the stress of the reinforcement to be transmitted to the concrete via support reactions, i.e. normal stresses, the permissible value of which is higher than that of the tangential stresses, and also allows not to lose contact between the surfaces of the concrete and the reinforcement during its Poisson narrowing. In this case, large intervals between the circle circumscribed around the cable section and the surface of the outer wires, which leave space for the formation of strong concrete ridges under the cable generatrix, and an increased enveloping contour are additional factors for increasing the bonding degree.

Furthermore, the known cable has an increased durability compared with the previous discussed prior art due to the surface contact between the wires, a smaller number of elements of periodic profile and their arrangement only in the areas of the wires extending to the outer surface of the cable and above the plastically compressed surface, which reduces the stress concentration when applying.

The disadvantage of the known cable design is the insufficient stability of high bonding degree, which is limited by the structural instability of the cable caused by the possibility of pressing one of the strand wires of the outer layer into a smaller radius between the strand wires of the inner layer with their sideways displacement during the cable passage along the pulleys and guides in the process of production, as a result of which the predetermined mutual position of the wires is lost and the outer surface of the cable loses the inclined surfaces that provide bonding through interlocking. Such a change in the cable configuration leads to a multiple decrease in its degree of bonding with concrete. Also, the local changes in the cable configuration lead to increased loads on the wires in the places where their mutual position changes, which negatively affects the durability and relaxation resistance of the cable.

The object of the invention is to develop such a reinforcing cable haying an increased degree of bonding, said cable having guaranteed structural stability and thus fully providing an increased degree of bonding with concrete, durability and relaxation resistance.

Said problem is solved by the fact that in a reinforcing cable having an increased degree of bonding, consisting of a central wire and strand Wires helically arranged around it in two concentric layers, wherein spiral grooves are provided on the central wire in the direction of the cable lay with a pitch equal to the pitch of the cable lay, and the strand wires of the inner layer are disposed in these grooves and each of them contacts the central wire and two adjacent strand wires of the inner layer, and three strand wires are helically arranged at equal intervals from one another in the outer layer, each of said wires being in contact with two adjacent strand wires of the inner layer, between which it is disposed in the groove. In this case, the most rational is the design of the cable with six strand wires of the inner layer, each of which is disposed in a groove on the surface of the central wire, and three strand wires of the outer layer.

The central wire provided with spiral grooves ensures a rigid fixation of the position of all the strand wires of the inner layer relative to the central wire and precludes the pressing of the strand wire of the outer layer between the wires of the inner layer with their sideways displacement. This ensures the stability of the required cable configuration.

In this case, the spiral grooves on the central wire can be provided both at equal and alternating larger and smaller intervals from one another.

The strand wires of the outer layer can be provided with a smaller section compared to the strand wires of the inner layer.

The spiral faces that are continuous along the length can be provided in the facing areas of the surface of the adjacent strand wires and in the outwardly facing areas of the surface of the strand wires of the inner layer. The spiral faces can also be provided in the outwardly facing areas of the surface of the strand wires of the outer layer.

A periodic profile can be provided on the surface of one or more strand wires. For example, the periodic profile can be in the form of inclined protrusions above the surface of the spiral faces in the outwardly facing areas of the surface of the strand wires.

In this case, the wires of the cable may have an anti-corrosion coating—for example, based on zinc.

The invention is explained by drawings.

FIG. 1 schematically shows an external appearance of a reinforcing cable having an increased degree of bonding of the structure 1+6+3;

FIG. 2 schematically shows a cross-section of the reinforcing cable of FIG. 1.

The reinforcing cable according to one of the embodiments of the invention is shown in FIG. 1-2. A straight central wire 1 is disposed along the axis of the cable and is configured with six spiral grooves 2 on the surface, in which six strand wires 3 of the inner layer are disposed, the wires tightly abutting on each other and on the grooves 2 of the central wire 1. In the intervals between the strand wires 3 of the inner layer, there are three strand wires 4 of the outer layer, the wires tightly abutting on the strand wires 3 of the inner layer. The areas of the surface of the strand wires 3 of the inner layer, being in contact with the surface of the adjacent strand wires 3 of the inner layer, and the strand wires 4 of the outer layer, as well as the areas of the surface of the strand wires 4 of the outer layer, being in contact with the surface of the strand wires 3 of the inner layer, are provided in the form of spiral faces 5, representing linear areas of the surface of said wires, having boundaries with the rest of the surface of said wires, visible with the naked eye. In the areas of the strand wires 3 of the inner layer and the strand wires 4 of the outer layer, extending to the outer surface of the cable, there are spiral faces 6 and 7, respectively, wherein each strand wire 3 of the inner layer has one spiral face 6, and each strand wire 4 of the outer layer has two spiral faces 7. On the surface of the strand wires 3 of the inner layer, a periodic profile in the form of protrusions 8 is applied over the generatrix of the spiral face 6.

The design of the reinforcing cable as described allows for maximum structural stability of the cable.

The reinforcing cable is manufactured as follows.

A wire 1 having spiral grooves 2 applied to the surface and circular section wires 3 and 4 are manufactured beforehand. During manufacturing the wires can be coated with an anti-corrosion coating, for example, based on zinc. Afterwards, the wires are laid together to form a cable using any known wire cable closing machine, for example, of a tow type. Directly in the centre of the cable laying it is subjected to reduction in a gage roller having inclined rollers rotating together with the rotor of the wire cable closing machine. As a result of the reduction, the wires are tightly pressed against each other and are deformed, while on the contacting surfaces of the strand wires 3 and 4 of the inner and outer layers, respectively, spiral faces 5 are formed, and on the surface of the cable at the points of interaction between the strand wires 3 and 4 and the gage rollers spiral faces 6 and 7 are formed, respectively. Simultaneously with cable reduction, a periodic profile in the form of protrusions 8 above the generatrix of the spiral face 6 is applied to the strand wires 3 of the inner layer.

Afterwards, the formed cable is tensioned up to a force of 30-80% of the breaking force by any known method, for example, between two capstans each of them being a set composed of a driving pulley and a non-drive pulley, or two driving pulleys. In the interval between the first and the second capstans when the reinforcing cable is in a straight tensioned state, it is heated up to the temperature of 370-430 degrees by means of an inductor, followed by forced cooling of the tensioned cable also in the interval between the first and the second capstans.

After cooling; is completed, the cable passes through the second capstan and reaches the storage, coil. After the wire is consumed by the wire cable closing machine on at least one of the coils installed in its rotor or on the external coil unwinding, the technological process is interrupted to fill the wire cable closing machine with wire, at the same time the storage coil is replaced with a similar empty storage coil, and the filled storage coil is shifted aside to the rewinding area, where the finished cable wound on a storage coil is rewound onto container coils or onto spools and packed by the known methods. 

1. A reinforcing cable having an increased degree of bonding, consisting of a central wire and strand wires helically arranged around it in two concentric layers, wherein spiral grooves are provided on the central wire in the direction of the cable lay with a pitch equal to the pitch of the cable lay, and the strand wires of the inner layer are disposed in these grooves and each of them contacts the central wire and two adjacent strand wires of the inner layer, and the strand wires are helically arranged at equal intervals from one another in the outer layer, each of said wires being in contact with two, adjacent strand wires of the inner layer, between which it is disposed in the groove.
 2. The reinforcing cable of claim 1, wherein it has six strand wires of the inner layer, each of which is disposed in a groove on the surface of the central wire, and three strand wires of the outer layer.
 3. The reinforcing cable of claim 1, wherein the spiral grooves on the central wire are provided at equal intervals from one another.
 4. The reinforcing cable of claim 1, wherein the spiral grooves on the central wire are provided at alternating larger and smaller intervals from one another.
 5. The reinforcing cable of claim 1, wherein the strand wires of the outer layer have a smaller section compared to the strand wires of the inner layer.
 6. The reinforcing cable of claim 1, wherein a spiral faces that are continuous along the length are provided in the facing areas of the surface of the adjacent strand wires, and the spiral hares are also provided in the outwardly facing areas of the surface of the strand and wires of the inner layer.
 7. The reinforcing cable of claim 6, wherein the spiral faces are also provided in the outwardly facing areas of the surface of the strand wires of the outer layer.
 8. The reinforcing cable of claim 1, wherein there is periodic profile on the surface of at least one strand wire.
 9. The reinforcing cable of claim 8, wherein the periodic profile is in the form of inclined protrusions above the surface of the spiral faces in the outwardly facing areas of the surface of the strand wires.
 10. The reinforcing cable of claim 1, wherein the wires have an anti-corrosion coating.
 11. The reinforcing cable of claim 1, wherein the main component of the anti-corrosion coating is zinc. 